I actually like getting FB through the mail. Not sure if I'd use the words "less durable", but most of mine have come through relatively well. Postcards will have dings and dents - all part of the process I guess and part of the quirks associated with the PE. Sure a FB might have the corners a little more dog eared sometimes, but I've received regular postcards in worse shape than some of the FB prints I've received.
Guess it all comes down to the carrier you use, the time of the year, who delivers it and whether there are 31 days in the month it arrives (or maybe that you post it?)